Limit question on a midterm that I have and still haven't the slightest idea on how to complete

Find all Values of a and b such that $\displaystyle \lim{x}\rightarrow{0}\frac{3sin(2x)+ax^{2}-bx}{x^2}=1$

all I could figure out was that if you use L'Hopitale's rule you would get

$\displaystyle \lim{x}\rightarrow{0}\frac{6cos(2x)+2ax+b}{2x}=1$

but I have no idea how to use this to solve for any variables

thank you